In my prior U.S. application Ser. No. 666,836, presently U.S. Pat. No. 4,057,074, a fluid power assistance control valve is described wherein an output member is provided with a blind bore for receiving an input member. Matching slots are provided on the input and output members for receiving a pair of projections which limit the rotation between the input and output members.
The projections cooperate with the input member and the output member to define fluid paths which communicate with an outlet. Fluid flow through the paths either increases or decreases, depending on the direction of rotation between the input and output members. Moreover, the projections cooperate with the input member and the output member to define reaction cavities which communicate with the fluid paths such that fluid communicated to one of the reaction cavities opposes the rotation of the input member.